Martin Höglund
Ben HoustonThe flight of NASA's Artemis (purple) uses two very close encounters with the moon's gravity (green) to changes its trajectory to get back to the earth (blue.) Amazing.
More details: https://www.nasa.gov/artemis-1
James Jefferies@BenHouston3D looks like it is going incredibly fast when it smashes back into the earth!
@jamesjefferies Interesting, you are correct, according to the speed in the bottom left, it will be doing 10km/s when it comes back to earth. Maybe it does another gravity type encounter, this time with earth, that kills its forward speed? Probably information on this somewhere online…
#OhMG 🌍🚀🌟@BenHouston3D @jamesjefferies
Re-entry speed is 24,500 mph in old money, which equates to 10.9 km per second.
Link: https://www.nasa.gov/specials/artemis-i/
Re-entry speed is 24,500 mph in old money, which equates to 10.9 km per second.
Link: https://www.nasa.gov/specials/artemis-i/
Similar re-entry speed to Apollo and about 1.5x re-entry speed of a shuttle. I wouldn't fancy it myself. Strictly ground crew!
herid@BenHouston3D @jamesjefferies The atmosphere will gradually slow it down. Apollo missions had similar reentry speeds.
https://en.wikipedia.org/wiki/Atmospheric_entry#Real_(equilibrium)_gas_model
https://en.wikipedia.org/wiki/Atmospheric_entry#Real_(equilibrium)_gas_model
embix@BenHouston3D @jamesjefferies Not sure they are doing that but aerobreaking seems an option to decrease apogee. A quick dive into the thinnest upper atmosphere can save a lot of delta v. And if time is no issue, you can repeat this as much as needed to decrease speed for safe (final) reentry.
Doohickie 
@jamesjefferies @BenHouston3D That's what retrorockets are for. They basically have to undo what the booster rockets did.
beyondwatts@BenHouston3D oh wow 🤩
Christopher League@BenHouston3D This is so amazing. I wonder if it's possible to also visualize where/when burns occur, or what proportion of the Δv along this path comes from lunar/earth gravity vs fuel expenditure… if that makes any sense.
Marius Gundersen - mdg 🌻@BenHouston3D orbital mechanics is weird
Jocelyn Sordoni@BenHouston3D just think of the maths involved in working this out!
\ˈthē-ˈˈärd-ˌvärk\@BenHouston3D This looks way more complex and far more interesting than the static images the BBC has been showing.
Jason Becker@BenHouston3D it’s pretty wild to watch this and think, “I technically know all of the math required to figure out how to do this, and yet, I never could put it together to do this.”
rhythmjones
Alex Barber@BenHouston3D That gravity assist to slow down after chasing the moon around its orbit for a bit is blowing my mind.
Loukas (They/Them) 🏳️⚧️@BenHouston3D I love this so much. Thank you for sharing 🌈
Howie Cohen@BenHouston3D that's a really cool animation, thx!
Clint "SpamapS" Byrum@BenHouston3D aaand now I have to reinstall Kerbal
Oleg "Ole" R. 🇱🇹🇨🇦🇺🇦@BenHouston3D Physics are awesome!
Luca 🤓@BenHouston3D as someone with >100 certified hours on KSP, I can confirm that this is how you do it
Dennis Faucher 
@BenHouston3D Very cool
Kyle KThis is so cool to see visualized.
Philip Steiner 🇨🇦 🚀Here's the formula:
🛰️ + 🌛 + 🌎 = 🤯
Granite T. Rock@BenHouston3D Kinda looks like a crash landing. I hope it brought a parachute! 😅
Alberto Cottica@BenHouston3D orbital mechanics: it works.
Pybonacci (no war)
Juan Luisthat second time where Artemis does the loop around the moon to change its trajectory to a perpendicular direction is amazing 👏 very elegant
lord pthenq1Nunca me va a dejar de asombrar la locura que es la navegacion con gravedad como la que hace Artemis. Es como un reloj, pero mas grande..
Neil Krey@BenHouston3D Thanks, Ben, for sharing this!
I have been trying to find a graphic of the mission, and am blown away by how different this is from the old Apollo flight path.
SomeGuyInSeattle@BenHouston3D Great illustration of orbital mechanics.
Astro Dad@BenHouston3D Just like KSP.
Kit Bashir@BenHouston3D @phocks Rich Parnell Sr is a steely-eyed missile man also
Simon Jackman@BenHouston3D in awe of the orbital mechanics at work here and the computation that must lie behind it. Did any of the Apollo missions employ moves like this?
Blippy the Wonder Slug (MOVED)@simonjackman @BenHouston3D Kinda, but no. There were animations used in broadcasts, but in those days, there was very little animation software available for the mainframes folks used (minis were just becoming a thing, and PCs were still under the horizon), and the animations were crude by today's standards. It had improved somewhat by the mid 70s, but there was little viewer demand for the later missions, when it had become "old hat."
Julian Doherty@BenHouston3D @simonjackman they wouldn’t have the computer power to plan this type of low delta-v manoeuvre back then.
Apollo craft were lobbed into position to burn into a nice circular orbit around the moon, stayed there, and then burned to come back. More defined mission phases using simpler one-body gravity calcs.
Artemis is doing a precise ballet with just a few nudges at the right time to send it on its way balancing gravity from Earth/Moon/Sun
Stephen Brooks 🦆@BenHouston3D I like the way it literally just falls down to Earth
Tim Y.C 🌐🌍@BenHouston3D how does it decrease its speed enough on the way back? Does it have that much thrust?
Aki Rodic@BenHouston3D this is called gravity assist right?
René ☀️ Hoffmann 
@BenHouston3D @aki gravity is a helluva force
Simon Detheridge 
@BenHouston3D I would *never* be able to pull this off in ksp
MarkD@BenHouston3D Fantastic graphic. Is it my imagination or does Artemis slow down on its first approach to the moon? That seems pretty weird. But then orbital mechanics is all weird, right 😃
@markd speed is listed in bottom left corner of graphics!
Island_Martha@BenHouston3D
Amazing! Had to watch that 3 times before I completely understood it.
Amazing! Had to watch that 3 times before I completely understood it.
Kyle Rose
Chris Warburton@BenHouston3D for those that haven’t tried it the app ‘space flight simulator’ allows you to model how real space dynamics work. Taught me a lot in understand how these orbital dynamics work (yes and without the maths 😀)
#WikiParty@BenHouston3D No doubt even more spectacular in 3D...
Dave@BenHouston3D the last moon encounter needs a *BONK* noise
Sunday@BenHouston3D They are using the Oberth effect in what is called a powered fly-by maneuver or also an Oberth maneuver. This means that with the same amount of momentum change (i.e. consumed fuel) it is possible to gain/lose much more kinetic energy, when being deep in a gravitational well (of the moon in this case).
Barbara TateI couldn't get my head around the static earth and moving moon model, I needed this digram!
J. Williams@BenHouston3D #space is awesome!
robpennoyer@BenHouston3D Awesome video. Would be cool to show an inset centered on the moon, to show the sphere of influence shift.
Michael Labowicz
matthewsmith@BenHouston3D this is so cool. Feels like space magic ... probably because the dots are, obviously, not quite to scale!
Matunos@BenHouston3D the three body solution
@matunos great book series you are alluding to! I loved it.
Rhett Rogers@BenHouston3D that is so cool. Then I see the pink dot go outside the green circle and I think, what if they just go flying off into space? They definitely need to get it right haha. Good thing there are people working there that are smarter than me
Greg (K8KET) 🇺🇸@BenHouston3D I'm in awe of the people who calculated these kinds of trajectories without the aid of computers back in the 60's and 70's.
@BenHouston3D I wonder how often this can be done before slowing the moon down ;)